We have studied the metabolism of pericyclocamphanone by P. Putida and have determined that oxidation occurs at the 6-position. This finding suggests that the Cytochrome P-450 cam system is not regiospecific, and two or more oxidation pathways with different energy requirements must exist. The lactonization of 18O camphor with cell free extracts of P. Putida is accompanied by exchange. By contrast, isotopic integrity is maintained during peracid oxidation. The mechanism of exchange in the enzymatic process is postulated to involve interaction of the oxygen in camphor with the carbonyl group of pterin in the enzyme substrate adduct. An equation relating the water solubility of organic non-electrolytes to molar volume has been derived. The equation has been verified with literature data on over one hundred compounds and is believed to be of predictive value.